1. Field of the Invention
The present invention relates to package structures and fabrication methods thereof, and more particularly, to a package structure having a MEMS (Micro-Electro-Mechanical System) element and a fabrication method thereof.
2. Description of Related Art
MEMS elements have integrated electrical and mechanical functions and can be fabricated through various micro-fabrication technologies. A MEMS element is generally disposed on a substrate and protected by a cover or an encapsulant from being damaged by external environment.
FIG. 1 is a schematic cross-sectional view of a conventional package structure having a MEMS element. Referring to FIG. 1, a MEMS element 11, such as a pressure sensing element, is disposed on an LGA (Land Grid Array) substrate 10, and electrical contacts 111 of the MEMS element 11 are electrically connected to electrical contacts 101 of the LGA substrate 10 by wire bonding. Then, a metal lid 12 is disposed on the substrate 10 to encase the MEMS element 11 therein, thus protecting the MEMS element 11 from being contaminated or damaged by external environment. However, such a package structure has a large size, which fails to meet the miniaturization requirement of end products.
Accordingly, FIG. 2 shows a wafer-level pressure sensing package structure as disclosed by US Patent Application Publication No. 2006/0185429. Referring to FIG. 2, a MEMS element 21, such as a pressure sensing element, is directly fabricated on a silicon substrate 23 and a glass lid 24 is bonded to the MEMS element 21 by anodic bonding.
However, in the silicon substrate 23, a sensing cavity 231 and a plurality of through holes 232 need to be formed. Therefore, a through silicon via (TSV) technique is required, which uses KOH as an etchant to form vias or grooves.
Compared with the previous package structure, the package structure disclosed by US Patent Application Publication No. 2006/0185429 has a greatly reduced size. However, the TSV technique is costly and requires a high degree of accuracy, thereby complicating the fabrication process and increasing the fabrication cost.
Therefore, there is a need to provide a package structure and a fabrication method thereof so as to overcome the above-described drawbacks.